linux-kernel - cpufreq pull req

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Date:	Thu, 29 May 2008 12:47:08 -0400
From:	Dave Jones <davej@...hat.com>
To:	Linus Torvalds <torvalds@...ux-foundation.org>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Linux Kernel <linux-kernel@...r.kernel.org>
Subject: cpufreq pull req

Please pull from ..
master.kernel.org:/pub/scm/linux/kernel/git/davej/cpufreq.git/ fixes

 cpufreq.c |    5 ++---
 1 file changed, 2 insertions(+), 3 deletions(-)

commit dca026139317dcbc642a30320d551f559692182f
Author: Lothar Waßmann <LW@...O-electronics.de>
Date:   Thu May 29 17:54:52 2008 +0200

    [CPUFREQ] fix double unlock of cpu_policy_rwsem in drivers/cpufreq/cpufreq.c
    
    In drivers/cpufreq/cpufreq.c the function cpufreq_add_dev() takes the
    error exit 'err_out_unregister' from different places once with the
    'cpu_policy_rwsem' lock held, once with the lock released:
    |		if (ret)
    |			goto err_out_unregister;
    |	}
    |
    |	policy->governor = NULL; /* to assure that the starting sequence is
    |				  * run in cpufreq_set_policy */
    |
    |	/* set default policy */
    |	ret = __cpufreq_set_policy(policy, &new_policy);
    |	policy->user_policy.policy = policy->policy;
    |	policy->user_policy.governor = policy->governor;
    |
    |	unlock_policy_rwsem_write(cpu);
    |
    |	if (ret) {
    |		dprintk("setting policy failed\n");
    |		goto err_out_unregister;
    |	}
    
    This leads to the following error message in case of a failing
    __cpufreq_set_policy() call:
    =====================================
    [ BUG: bad unlock balance detected! ]
    -------------------------------------
    swapper/1 is trying to release lock (&per_cpu(cpu_policy_rwsem, cpu)) at:
    [<c01b4564>] unlock_policy_rwsem_write+0x30/0x40
    but there are no more locks to release!
    
    other info that might help us debug this:
    1 lock held by swapper/1:
     #0:  (sysdev_drivers_lock){--..}, at: [<c018fd18>] sysdev_driver_register+0x74/0x130
    
    stack backtrace:
    [<c002f588>] (dump_stack+0x0/0x14) from [<c00692fc>] (print_unlock_inbalance_bug+0xc8/0x104)
    [<c0069234>] (print_unlock_inbalance_bug+0x0/0x104) from [<c006b7ac>] (lock_release_non_nested+0xc4/0x19c)
     r6:00000028 r5:c3c1ab80 r4:c01b4564
    [<c006b6e8>] (lock_release_non_nested+0x0/0x19c) from [<c006b9e0>] (lock_release+0x15c/0x18c)
     r8:60000013 r7:00000001 r6:c01b4564 r5:c0541bb4 r4:c3c1ab80
    [<c006b884>] (lock_release+0x0/0x18c) from [<c0061ba0>] (up_write+0x24/0x30)
     r8:c0541b80 r7:00000000 r6:ffffffea r5:c3c34828 r4:c0541b8c
    [<c0061b7c>] (up_write+0x0/0x30) from [<c01b4564>] (unlock_policy_rwsem_write+0x30/0x40)
     r4:c3c34884
    [<c01b4534>] (unlock_policy_rwsem_write+0x0/0x40) from [<c01b4c40>] (cpufreq_add_dev+0x324/0x398)
    [<c01b491c>] (cpufreq_add_dev+0x0/0x398) from [<c018fd64>] (sysdev_driver_register+0xc0/0x130)
    [<c018fca4>] (sysdev_driver_register+0x0/0x130) from [<c01b3574>] (cpufreq_register_driver+0xbc/0x174)
    
    Signed-off-by: Lothar Waßmann <LW@...O-electronics.de>
    Signed-off-by: Dave Jones <davej@...hat.com>

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